1. Field of the Invention
The present invention relates to a driver/receiver pair ("transceiver") which allows simultaneous bidirectional communications. More specifically, a system is provided which allows a first driver/receiver circuit to concurrently communicate signals between a second driver/receiver circuit.
2. Description of Related Art
Transceivers which bidirectionally and simultaneously send information between different driver/receiver circuits along a transmission line are known in the art. However, these circuits have heretofore been implemented using bipolar technology. Bipolar logic is also referred to as transistor-transistor logic. In bipolar logic, a digital signal technique is used wherein a positive voltage signal and ground is alternated between a negative voltage signal and ground. Thus, multiple voltage sources are required for this type of technology to be implemented.
Complementary method oxide semiconductor (CMOS) technology pairs transistors together which complement one another and use varying positive voltage swings to activate/deactivate the circuits causing a logical "1" and/or logical "0" to be communicated to one another. Due to the positive and negative voltage requirements of bipolar circuits, multiple separate voltage sources are needed to implement this technology.
U.S. Pat. No. 3,612,781 describes simultaneous bidirectional transmission system using bi-polar circuits which require voltage differences of both above and below a reference voltage, as shown in FIGS. 2 and 3, thus requiring multiple voltage sources.
U.S. Pat. No. 5,216,667 discusses a bi-polar simultaneous bidirectional transceiver which utilizes a plurality of positive and negative voltage sources, i.e. Vcc, Vee, Vr, Vt and Vx.
It can be seen that none of the prior art systems utilize a CMOS driver/receiver pair which can simultaneously send and receive information in a single transmission line using only a single voltage source. Thus, a need exists for a communications system, such as the present invention, which allows information to be bidirectionally and simultaneously transmitted and received on a single line, while using only a single voltage source, thereby allowing circuits with significantly less electrical power and cooling requirements.